Welcome to

"Our bookcase"

by HOLTES & SIETSMA

The official website of the BACK-UP trilogy, written by Dutch author duo Bert Holtes & Wop Sietsma.

This gripping thriller series is packed with suspense, intrigue, action, mysteries, and shocking revelations — and is already beingread in over 100 countries worldwide.

To give you a taste of our story, we’re offering the first twobooks as free e-books —not just for you to read, but also to share!

Dive into this unique trilogy and experience an unforgettablereading adventure.

Enjoy reading!